In most power delivery systems it is important that the system be robust enough to ensure uninterrupted service despite failure events that occur in a portion of the power delivery system. For example, in naval platforms, such as a warship, the survivability of a system often depends on the ability of the integrated power system (IPS)—used to distribute power to various systems throughout the ship including control, propulsion, and combat systems, as well as ship service loads—to withstand the occurrence of multiple failures (or faults).
Survivability is the ability to provide power for consumers/loads under multiple faults caused by natural or hostile disruptions. Failure of a single IPS level, such as the generator bus, to supply power to the rest of the IPS will immediately result in failure of the entire IPS. Power interruption, let alone total power loss, would most certainly lead to mission failure, possibly complete destruction of the ship, as well as personnel and economic losses.
Failure events or “faults” include the loss of a cable or generator. Faults can be caused by direct hits or as a result of secondary or cascading damage. Each fault is considered an event that may not be repaired during battle. Thus, multiple faults are viewed as independent events and considered to be simultaneously occurring in that each fault persists until repair is possible and achieved. If after the faults have occurred, the generator bus is still able to supply power produced by all generators to the rest of the IPS and no response is required, then the generator bus is said to survive the given number of faults without requiring IPS reconfiguration. If power supplied from the generator bus to the rest of the IPS is reduced either due to damage of at least one generator or due to faults in cables isolating at least one generator, then the generator bus is said to survive requiring IPS reconfiguration.
Up to now, increases in IPS survivability have mostly been achieved through generator redundancy. However, in the design of a ship (or other vehicle) or a power distribution system, cost, weight, and spatial separation of generators limit this option. Reconfiguration is commonly viewed as a tool for ensuring uninterrupted power supply to ship loads. However, the act of reconfiguration itself entails a cost and delay. For instance, reconfiguration activities may interfere with activities of other ship systems, because they require ship control and communication resources to analyze faults, reroute paths, and perform switch-over operations. Electrical transients induced by switch-overs may hinder operations or even damage equipment. Further, the survivability of a power delivery system cannot exceed that determined by the topological limitations of the system. Therefore, the power delivery system's survivability is limited by the topological constraints of the system.